1. Field of the Invention
This invention relates generally to telecommunications and more specifically, to switches of a telecommunications network that transport and process the Charge Number, Calling Party Number, and Presentation Indicator elements of Automatic Number Identification information to deliver Caller ID information across the network.
2. Related Art
A typical telecommunications network comprises multiple telecommunication switches located throughout a geographical area. FIG. 1 illustrates such a typical telecommunications environment. An originating party 102 utilizes a telephone 104 to place a call. The call is routed to an origination switch 108 on a transmission line referred to as the originating trunk. The originating trunk is one of many transmission lines coming into the origination switch 108 from the same geographical location as the telephone 104. These transmission lines including the originating trunk is referred to as an origination trunk group 106. After processing an incoming call, the switch transmits the call to a destination switch 114. The call is transmitted over a transmission line (referred to as the intermatching trunk) to the destination switch 114. Similar to the originating trunk, a terminating trunk 110 is one of a group of trunks connecting the destination switch 114 to a local exchange carrier (LEC), public branch exchange (PBX) or a caller identification (ID) box 116, which is, in turn, connected to a receiving telephone 118. Thus the Caller ID information is available before the first ring and a receiving party 120 can know the telephone number of the originating party 102 before actually picking up the telephone receiver to answer the incoming call.
At times, the originating party 102 may not want the receiving party to have the Caller ID information for privacy reasons. Therefore the origination switch 108 must transport a Presentation Indicator (PI) across the network to the destination switch 114. The PI indicates whether the originating party's 120 telephone number may be presented, via Caller ID, to the receiving party 120 ("Address Presentation Allowed") or must remain private ("Address Presentation Restricted"). The PI is defaulted to the "Address Presentation Allowed" setting, but may be set to "Address Presentation Restricted" by the originating party 102 before placing the call. This is usually done by dialing a certain prefix (e.g., "*67") before placing the call.
Automatic Number Identification (ANI) information is encoded on every incoming call, which box 116 can decipher. ANI information is comprised of the Calling Party Number (CgPN) parameter, the Charge Number (ChgN) parameter, and PI information. The CgPN is the information that identifies the number of the originating party and the ChgN is the actual telephone number charged for that particular phone call. In normal home dialing, these two parameters are identical. However, when dealing with a Private Branch Exchange (PBX (i.e., several business lines in a building), the ChgN may be the owner of the services, and thus not the same as the CgPN who is the subscriber of the services behind the PBX.
There are many switch and trunk group types, each having their own configurations and protocols with different message formats for transmitting switch signaling and voice data. Types include: (a) Signaling System Seven/Integrated Services Digital Network User Part (SS7/ISUP) which is a phone out-of-band signaling protocol system that allows a greater bandwidth by separating the phone signaling (supervising, alerting, and addressing functions) and voice data; (b) Integrated Services Digital Network/ Primary Rate Interface (ISDN/PRI), which is an out-of-band 1,544,000 bits/sec network that combines voice, data, signaling, etc., and operates on a T-1 line; and (c) Per Trunk Signaling (PTS) Inband which is a tone signaling system that passes within the same band as voice data. The origination trunk group 106 and termination trunk group 110 may be the same or different trunk types, thus effecting Caller ID delivery.
The different protocols for the above mentioned trunk group types are well known in the art. For example, the SS7/ISUP trunk type uses an Initial Address Message (IAM) to send the ChgN, CgPN, and the PI as parameters in the message from the origination switch 108 to the termination switch 114. The format of this message is defined in American National Standards Institute, Inc. (ANSI) ISUP Issue 1, T1.113-1988 (which is incorporated herein by reference). A typical IAM format is shown below in Table 1:
TABLE 1 ______________________________________ Parameter Type Length ______________________________________ Message Type F 1 Nature of Connection Indicators F 1 Forward Call Indicators F 2 Calling Party's Category F 1 User Service Information V 3-n Called Party Number V 2-11 Access Transport O 3-n Business Group O 9-n Call Reference O 8 Calling Party Number O 5-12 Charge Number O 3-14 Circuit Assignment Map O 6 Generic Address O 6-13 Generic Digits O 4-n Forward Call Special Information O 3 Multiple Business Group O 9 Network Specific Facility O 3-n Operator Information O 9-n Software Indicator O 3 Supplementary Line Information O 3-n Network Transport O 5-n Originating Line Information O 3 Redirection Information O 3-4 Transit Network Selection O 5-6 ______________________________________
A typical CgPN parameter, which includes the Presentation Indicator as a subparameter, format is shown below in Table 2:
TABLE 2 ______________________________________ Byte 7 6 5 4 3 2 1 0 ______________________________________ 1 Parity Nature of Address Indicator 2 Spare Numbering Plan PI SCREENING 3 D2 D1 4 D4 D3 : : : n-1 D(m-2) D(m-3) n Dm (or filler) D(m-1) ______________________________________
The CgPN parameter includes some of the following data elements:
Parity--This field is a parity indicator which shall be coded as follows:
______________________________________ 0 Even number of Dm digits; 1 Odd number of Dm digits; ______________________________________
Nature of Address Indicator--this field defines the type of data identifying the call originator;
PI--the Address Presentation Restricted Indicator specifies whether the originating address may be disclosed or must be kept confidential. Coding is as follows:
______________________________________ 00 Address presentation allowed (default); 01 Address presentation restricted; 10 Address unavailable due to interworking; 11 Spare/Reserved; ______________________________________
D1 to Dm--These subfields are digits representing the value of the calling party number type specified in the indicator field. Each digit (0 to 9) occupies 4 bits, encoded in BCD format.
The typical Charge Number Parameter format is shown below in Table 3:
TABLE 3 ______________________________________ Byte 7 6 5 4 3 2 1 0 ______________________________________ 1 Parity Nature of Address Indicator 2 Spare Numbering Plan Reserved 3 D2 D1 4 D4 D3 : : : n-1 D(m-2) D(m-3) n Dm (or filler) D(m-1) ______________________________________
Similarly, the ISDN/PRI trunk group type uses a SETUP message containing the appropriate data elements to delivery ANI information. Also, PTS/Inband trunk types implement a variety of protocols to delivery of ANI information. These vary according to manufacturer and are also well known in the art.
Current implementations for Caller ID delivery map the ChgN parameter to the CgPN parameter and deliver that information to the receiving party 120 as the CgPN. This mapping is done at the origination switch 108 and thus limits the information available at the destination switch 114 and consequently to the receiving party 120.
The Federal Communications Commission (FCC) has recently required that Local Exchange Carriers (LECs) (i.e., local telephone service companies) and Interexchange Carriers (IXCs) (i.e., long distance telephone service companies) to transmit the CgPN and honor the PI, where the information is available, for all SS7/ISUP calls. Therefore there is a need to comply with these orders but still provide the ability to map the ChgN to the CgPN. Furthermore, there is a need, to allow different telephone subscribers to choose different Caller ID delivery options based on the data available, the PI, and the origination/termination trunk group types without impacting current implementations for billing and switch call processing.